The present invention relates to analytical instruments for detecting hazardous materials, and in particular to portable instruments.
This invention relates to analytical devices and, more specifically, to devices for detecting and analyzing trace concentrations of contaminants in a gaseous medium, such as air. A portable analytical system and method combining chromatography and an array of electrochemical sensors is disclosed in the copending U.S. application of Solomon Zaromb and Joseph R. Stetter, Ser. No. 881,310, filed July 2, 1986, entitled "Portable System and Method Combining Chromatography and Array of Electrochemical Sensors (Docket S-64,127) and assigned to the assignee of the present invention, the disclosure of which application is incorporated herein by reference. While a variant of that system, comprising a liquid chromatograph, has provided effective identification and concentration measurement of several hazardous contaminants in liquid samples, it has been found that the detection of very low or trace concentrations of these contaminants in air samples by that system requires a high degree of preconcentration into a small volume of liquid.
The use of absorbents, such as charcoal or Tenax for preconcentrating in gas chromatography has several objectionable features, including the necessity for time-consuming and somewhat complicated desorption and sorbent-reconditioning steps and possible introduction of interfering contaminants from the sorbents. The use of cryogenic methods of preconcentration have been attempted, but are seriously limited by the necessity to use a sample volume of only about 10 cc to achieve 100% collection efficiency. The use of such a small sample volume means that the lower detection limit for contaminants of interest is about 1 ppb (part per billion) in air. It would be desirable to have about 100 times lower detection limits for certain contaminants of interest, e.g. the highly mutagenic two- and three-ring primary aromatic amines, such as the anthracyl-amines.